Submission #1092852

#	Time	Username	Problem	Language	Result	Execution time	Memory
1092852		juicy	Network (BOI15_net)	C++17	100 / 100	301 ms	61524 KiB

net

#include <bits/stdc++.h>

using namespace std;

#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif

int main() {
  ios::sync_with_stdio(false); cin.tie(nullptr);

  int n; cin >> n;
  vector<vector<int>> g(n);
  for (int i = 1; i < n; ++i) {
    int u, v; cin >> u >> v; --u, --v;
    g[u].push_back(v);
    g[v].push_back(u);
  }
  vector<int> cnd;
  function<void(int, int)> dfs = [&](int u, int p) {
    if (g[u].size() == 1) {
      cnd.push_back(u + 1);
    }
    for (auto v : g[u]) {
      if (v ^ p) {
        dfs(v, u);
      }
    }
  };
  dfs(1, 1);
  if (cnd.size() & 1) {
    cnd.push_back(cnd[0]);
  }
  int m = cnd.size() / 2;
  cout << m << "\n";
  for (int i = 0; i < m; ++i) {
    cout << cnd[i] << " " << cnd[i + m] << "\n";
  }
  return 0;
}

• Subtask 1: 18 / 18
• Subtask 2: 45 / 45
• Subtask 3: 37 / 37